Marginal fit of semi-direct restorations made with different types of composite resin, with or without preheating, and obtained in models from different associations of impression materials

Abstract

When extensive cavities in posterior teeth are present, the direct restorative approach is particularly difficult in cases where the cavity extensively involves the interproximal surface and gingival margin. However, the adaptation of semi-direct restorations depends on some factors related to the restorative material, the restorative technique and the associated impression materials. Thus, the aim of this study will be to evaluate the marginal fit of semi-direct restorations made on models obtained from the combination of different elastic impression materials in the first stage, and the influence of preheating composite resins on the marginal fit in the second stage. In the first stage, this in vitro study presents as a variation factor the association of impression materials at 7 levels (n=8): Alginate mold (Hydrogum, Zhermack, Germany) + Addition Silicone model (Express" XT, 3M ESPE - USA); Alginate mold + Condensing Silicone model (Zetaplus Kit - Zhermack, Germany); addition silicone mold + condensation silicone model; condensation silicone mold + addition silicone model; Alginate mold + Addition Silicone for models (Die Silicone, VOCO GmbH, Germany); Addition silicone mold + Die Silicone model; Condensation silicone mold + Die Silicone model. All models obtained will be restored with Filtek" Z250 XT microhybrid resin (3M ESPE, USA) with the standardized incremental technique and the response variable will be the external marginal adaptation at 3 predetermined points per tooth. In the second stage, the combination of impression materials that presents the best marginal adaptation in the first stage will be used, and 3 composite resins will be evaluated, with or without preheating (n=8): Filtek" Z250 XT (3M ESPE, USA), Filtek" Z350 XT (3M ESPE, USA) and Filtek" One Bulk Fill (3M ESPE, USA). To obtain the specimens in both stages, prefabricated resin molars with extensive preparations for onlay restoration (P-occlusal, São Paulo, Brazil) will be used, which will be previously flattened on the occlusal surface in order to standardize the volume of the restoration. Flattened molars will be molded and restored with different impression materials and composite resins. The semi-direct restorations will be made on the resulting models and after cementation on the respective prepared molars, the marginal adaptation will be evaluated with the aid of a portable digital microscope. The results of the mean marginal fit of each tooth will be subjected to specific statistical analysis (p<0.05) in both studies. (AU)